From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7762CC43381 for ; Sun, 31 Mar 2019 18:47:49 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4A06C2085A for ; Sun, 31 Mar 2019 18:47:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HQONUDrm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4A06C2085A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=g2NVdvQTARUaCGQiXyorPmjhHwpm3372zS2yihNiUjU=; b=HQONUDrmrhvC7b tSUwoZnW42U2v3LLMcyoK11R5pl8rsm/d/WyiXhXnCvFhq8N3vxrQdy9F99p8muz1f54LjsWIkwWy Uly7YROVjCSqzqFOOD6aWArlST65NocHmASB+TlI8bkI1ic0jRQxmn9n3r74SYOLu0qyiRMRXKm6K 1/EUuC8yptJh1lxrPTJgd5uENUiebulyhbNlb1ErAvlZ/GkS6arQDLVxOxYUsddR1r3qZJ5bwSWFM xQqv2FyZDrZSLJBkvOUwZzmT0ykGuyuJlA70qfLDv1RSOta4ugQ+AH2xArD3tTqxKLsug9veUl5ti Iz8O5V8XUrZf9UF/3D0g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hAfUb-0004Dm-F7; Sun, 31 Mar 2019 18:47:41 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hAfUX-000453-0Y for linux-amlogic@lists.infradead.org; Sun, 31 Mar 2019 18:47:39 +0000 Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hAfUR-0007FK-3o; Sun, 31 Mar 2019 20:47:31 +0200 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1hAfUQ-0001eS-E9; Sun, 31 Mar 2019 20:47:30 +0200 Date: Sun, 31 Mar 2019 20:47:30 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Martin Blumenstingl Subject: Re: [PATCH 0/1] pwm: meson: fix scheduling while atomic issue Message-ID: <20190331184730.y767dxhblffxj3om@pengutronix.de> References: <20190324220217.15813-1-martin.blumenstingl@googlemail.com> <20190325084153.l44pzfewcqlkoaoe@pengutronix.de> <20190325200730.cx73jgxfexz6ybzq@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-amlogic@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190331_114737_271094_76CD073C X-CRM114-Status: GOOD ( 15.36 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pwm@vger.kernel.org, Neil Armstrong , linux-kernel@vger.kernel.org, thierry.reding@gmail.com, kernel@pengutronix.de, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, jbrunet@baylibre.com Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On Sat, Mar 30, 2019 at 08:29:35PM +0100, Martin Blumenstingl wrote: > Hello Uwe, > = > On Mon, Mar 25, 2019 at 9:07 PM Uwe Kleine-K=F6nig > wrote: > [...] > > > > - Does stopping the PWM (i.e. clearing MISC_{A,B}_EN in the MISC_AB > > > > register) freeze the output, or is the currently running period > > > > completed first? (The latter is the right behaviour.) > > > I don't know, I would have to measure this with a logic analyzer. > > > > In practise you can do this with a multimeter, too. Just do something > > like: > > > > pwm_apply_state({ .enabled =3D true, .period =3D 5s, .duty_cycl= e =3D 5s, .polarity =3D PWM_POLARITY_NORMAL }); > > pwm_apply_state({ .enabled =3D false, .period =3D 5s, .duty_cyc= le =3D 5s, .polarity =3D PWM_POLARITY_NORMAL }); > > > > (assuming the PWM supports periods that long). The expectation is that > > the last command takes nearly 5 s to complete and while it waits the > > output is high and on return it's low. If that isn't the case, there is > > a bug somewhere. > the longest supported period (using the 24MHz crystal as input, which > is the slowest input clock and thus gives the longest possible > duration) is 349514407ns (that's approx. 0.35 seconds). my multimeter > isn't fast enough to measure this so I'm using my logic analyzer with > puleseview instead: [0] > = > I added the following code to meson_pwm_request: > struct pwm_state enable =3D { > .enabled =3D true, > .period =3D 349514407U, > .duty_cycle =3D 349514407U, > .polarity =3D PWM_POLARITY_NORMAL }; > struct pwm_state disable =3D { > .enabled =3D false, > .period =3D 349514407U, > .duty_cycle =3D 349514407U, > .polarity =3D PWM_POLARITY_NORMAL }; > pwm_apply_state(pwm, &enable); > pwm_apply_state(pwm, &disable); > = > this returns immediately. my logic analyzer doesn't see signal change > (I'm sampling at 1MHz). > = > can you please confirm that my test code and measurement procedure is cor= rect? > if it is then my observation is that disabling the PWM does so > immediately, without waiting for the current period to complete Ack, with the above two pwm_apply_state the output must be high when the first pwm_apply_state returns. Then it must stay high for n * 349514407 ns (for an natural n >=3D 1) and then go low. Best regards Uwe -- = Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | http://www.pengutronix.de/ | _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic